And while savings accounts can be great for short-term goals, they're not ideal if you're putting money away for longer term goals, like retirement or a house. That's because, if your money is in a traditional savings account, you're probably earning less than inflation, which is how the price of everyday goods increases steadily over time. It's why something that cost $5 in 1980 usually costs just over $15 today.

"What they don't realize and what nobody really tells you is that money is invisibly losing value," Sethi says.

The only way to 'truly grow' your money

Over the long term, the only way to "truly grow that money" is to invest it, Sethi says.

But investing doesn't have to complicated or scary, Sethi says. "I log in into my investing account about once a month and I spend less than an hour a month on investing," he says. "It just works automatically."

Your investments should be "low cost and long term," he says. Instead of picking an individual stock, look for a low-feeindex fund that tracks the market. This is an approach that's backed by many of the top financial experts and investors, including Warren Buffett.

"Consistently buy an S&P 500 low-cost index fund," he told CNBC's On The Money. "I think it's the thing that makes the most sense practically all of the time."

If you don't want to set up a brokerage account and pick a fund on your own, there are robo-advisors that will guide you through the process. Services like Betterment and WiseBanyan let you start investing with just $1.

"The true way to grow your money is not just to save it," says Sethi. "That's a start, but I want you to go further and start investing."